Flyback power converters are one of the most widely used types of power converters that are used for providing appropriate supply voltage or supply current in industry and consumer electronic devices. Flyback power converters generally adopt primary feedback control technique to reduce cost.
In most offline power applications, when entered into sleep mode, the switching frequency of a flyback converter should be decreased to be lower than 100 HZ to reduce power loss. However, only decreasing the switching frequency normally cannot meet the requirements of low standby (sleep mode) power dissipation and low noise for most offline flyback converters. Therefore, it is desired to further reduce the maximum current that is allowed to flow through a power switch in the primary side of a flyback converter to reduce the standby power dissipation and noise.